Response of phytoplankton to an experimental fish culture in net cages in a subtropical reservoir / Resposta do fitoplâncton ao cultivo experimental de peixes em tanques-rede em um reservatório subtropical

Abstract This study aimed to evaluate nutrients concentration and spatial-temporal changes in phytoplankton biovolume during an experimental fish culture in net cages in a lateral arm of Salto Caxias reservoir, Brazil. Two sampling stations were placed in the affected lateral arm and other two in a cageless lateral arm. Neither abiotic variables nor phytoplankton biovolume presented significant differences between the treatments. Only temporal changes were confirmed by the analysis performed. Both lateral arms were classified as oligotrophic, reflecting low influence of the net cages. Phytoplankton growth seems to be limited by nitrogen. Biovolume values were, in general, low and five major functional groups were recognized (E, F, G, K and P). In summer higher biovolume values were observed and representatives of Chlorophyceae and Cyanobacteria belonging to the functional groups F and K, respectively, were the most important. In winter phytoplankton was mainly composed by Bacillariophyceae taxa from P group. G group was also restricted to winter and E group occurred in winter and summer. The variations recorded in phytoplankton structure appear to have been mainly influenced by seasonal changes in temperature, precipitation and nutrients availability. The effects of net cages on the abiotic variables and phytoplankton biovolume appear to have been small, probably due to the small number of net cages employed and the system dilution capacity. However, a permanent monitoring of phytoplankton is recommended, since this environment has a carrying capacity, from which the trophic state may increase.

Resumo Este estudo objetivou avaliar alterações nas variáveis abióticas e no biovolume fitoplanctônico durante o cultivo experimental de peixes em tanques-rede em um braço lateral do reservatório de Salto Caxias, Brasil. Foram selecionadas duas estações de amostragem no braço com tanques-rede e outras duas em um braço sem tanques. As variáveis abióticas e o biovolume fitoplanctônico não apresentaram diferenças significativas entre os locais estudados. Apenas mudanças temporais foram confirmadas pelas análises utilizadas. Os dois braços laterais foram classificados como oligotróficos, refletindo a baixa influência dos tanques-rede. O crescimento do fitoplâncton parece ter sido limitado principalmente por nitrogênio. Os valores de biovolume foram, em geral, baixos e cinco principais grupos funcionais foram observados (E, F, G, K e P). No verão, os maiores valores de biovolume foram observados e representantes de Chlorophyceae e Cyanobacteria dos grupos funcionais F e K, respectivamente, se destacaram. No inverno, o fitoplâncton foi composto principalmente por táxons de Bacillariophyceae do grupo P. O grupo G também foi restrito ao inverno e o grupo E ocorreu no inverno e verão. As variações registradas na estrutura do fitoplâncton parecem ter sido principalmente influenciadas pelas mudanças sazonais de temperatura, precipitação e disponibilidade de nutrientes. Os efeitos dos tanques-rede sobre as variáveis abióticas e biovolume fitoplanctônico parecem ter sido pequenos, provavelmente devido ao pequeno número de tanques utilizados e a capacidade de diluição do sistema. Entretanto, o monitoramento permanente do fitoplâncton é recomendado, uma vez que este ambiente possui uma capacidade de suporte, a partir da qual o estado trófico pode aumentar.

Chlorophyll a and turbidity patterns over coral reefs systems of La Parguera Natural Reserve, Puerto Rico

Abstract:Studies of temporal and spatial changes in phytoplankton biomass and turbidity provide essential information on coral reef ecosystem function and health.Fluctuation of phytoplankton biomass responds to several factors including nutrient inputs,both anthropogenic and natural,while turbidity is mostly affected by sediment resuspension or transport from terrestrial systems.These parameters can be used as sentinels of significant environmental factors "modifying "coral reef systems.A chlorophyll a concentration (Chl a )and turbidity (Turb)in situ logger was installed at 10 stations from June 4 to July 7,2003 in La Parguera Natural Reserve (Southwestern Puerto Rico)to assess short-term temporal and geographic variation in patterns of phytoplankton biomass and turbidity at pre-selected sites as part of an interdisciplinary long-term study.Average station Chl a variation was 0.17-1.12 µg l-1 and 0.2-23.4 NTU for Turb.Results indicate that the western near-coastal stations had higher levels of Turb and Chl a .The easternmost mid shelf station,Romero reef,was similar to coastal stations probably due to nutrient and suspended sediment inputs from a source external to our study area to the east,Guánica Bay.Comparisons between different sampling days indicate significant differences between days for most stations suggesting that one-time discrete sampling may not be representative of average water column conditions and illustrate the dynamic nature of coral reef systems.Further work is warranted to assess seasonal changes that integrate short-term (daily)variability in both Turb and Chl a.

Fitoflagelados potencialmente tóxicos y nocivos de costas del Pacífico mexicano / Potentially toxic and harmful phytoflagellates from the Mexican Pacific coasts

Los fitoflagelados son un grupo heterogéneo de flagelados autotróficos, heterotróficos y mixotróficos, con importancia ecológica para los niveles tróficos en diferentes ecosistemas. Los fitoflagelados en costas del Pacífico mexicano (y en Latinoamérica en términos generales) son virtualmente desconocidos, sólo se tienen pocos registros. El estudio de los fitoflagelados requiere de métodos complicados de recolección y análisis. Esta es, probablemente, la causa de la escasez de conocimiento de este grupo en áreas tropicales y subtropicales. Material recientemente recolectado a lo largo del Pacífico mexicano sirvió para el estudio de fitoflagelados marinos, incluyendo algunos tóxicos y potencialmente tóxicos. Se usaron muestras de plancton filtradas por gravedad y con bomba de vacío utilizando diferentes métodos de fijación y análisis. Se registran aquellas especies presentes o con posibilidad de estarlo que son potencialmente nocivas para el ecosistema marino pertenecientes a los Phyla Euglenophyta, Heterokontophyta y Haptophyta. Estas especies están distribuidas en el plancton, en aguas oceánicas y costeras

The phytoflagellates are a heterogeneous group of autotrophic, heterotrophic and mixothrophic flagellates of trophic importance in several ecosystems. As in the rest of Latin America, the phytoflagellates that occur in the Mexican Pacific coasts are virtually unknown except for a few records. Their study require complicated collection and analysis methods, a probable cause for the scarce knowledge of this group in tropical and subtropical areas. Material recently collected from various localities along the Mexican Pacific coasts was used to study phytoflagellates, including toxic and potentially toxic species. Plankton samples were treated by gravity and pump filtration, using different methods for fixation and analysis. The phyla Euglenophyta, Heterokontophyta and Haptophyta were found. They occur as plankton in oceanic and shallow coastal waters

Proliferaciones algales nocivas de cianobacterias (Oscillatoriaceae) y dinoflagelados (Gymnodiniaceae) en el Golfo de Nicoya, Costa Rica / Harmful blooms of cyanobacteria (Oscillatoriaceae) and dinoflagellates (Gymnodiniaceae) in the Golfo de Nicoya, Costa Rica

Recently, the Pacific coast of Costa Rica has experienced an increase in both magnitude and frequency of harmful algae blooms (HAB). The lack of data regarding the dynamics of these events in the area, and the species of microalgae that produce them, are themes of great interest. The blooms have produced negative impacts on fishery resources and on human health in Costa Rica. In May 2002 a HAB left a large number of dead fish along the central Pacific coast. Water samples were collected using a phytoplankton net and fixed for subsequent processing by electron microscopy. In addition, a one liter sample of surface water was taken for later cell count. In the observed HAB, the dominating organisms found were the cyanobacteria Trichodesmiun erythraeum surrounded by high concentrations of Gram - bacteria and the dinoflagellate Cochlodinium cf. polykrikoides. T. erythraeum, is one of the most important N 2 fixing cyanobacteria in marine waters that has been associated with HAB events in diverse parts of the world as well as with symptoms that produce contact dermatitis and other discomforts. C. cf. polykrikoides is a dinoflagellete associated with fish kills; although the type of associated toxins are unknown. In a national newspaper 17 cases of intoxication in humans were reported during this same period, which presented respiratory disorders and burning of the eyes. This is the first report in Costa Rica where a cyanobacteria and a dinoflagellate were observed together producing HAB

Recientemente, la costa del Pacífico de Costa Rica ha experimentado un aumento en magnitud y frecuencia de proliferaciones algales nocivas (PAN). La falta de datos con respecto a la dinámica de estos eventos en el área, y las especies de microalgas que los producen, son temas de mucho interés. Las PAN han producido impactos negativos en los recursos pesqueros y en la salud humana en Costa Rica. En mayo de 2002, una PAN se observó frente a las playas a lo largo del Pacífico central; además, se observó un gran número y diversidad de peces muertos. Las muestras de agua fueron recolectadas usando una red de fitoplancton y se fijaron para ser procesadas posteriormente con microscopía electrónica. Asimismo, se tomó un litro de muestra de la superficie para su posterior conteo celular. En la PAN observada, los organismos dominantes fueron la cianobacteria Trichodesmiun erythraeum, rodeada por altas concentraciones de bacterias Gram -, y el dinoflagelado Cochlodinium cf. polykrikoides. T. erythraeum, es una de las principales cianobacterias fijadoras de N2 atmosférico en aguas marinas, y se ha asociado con los eventos PAN en diversas partes del mundo, produciendo síntomas como dermatitis por contacto con la brisa marina y otras afecciones. C. cf. polykrikoides es un dinoflagelado asociado con mortalidad de peces; aunque el tipo de toxinas asociadas aún es desconocido. En un periódico nacional se reportaron 17 casos de intoxicación en humanos durante este mismo periodo de PAN, los afectados presentaron desórdenes respiratorios e irritación en los ojos. Éste es el primer informe en Costa Rica dónde se observaron cianobacterias y dinoflagelados juntos produciendo PAN. Este tipo de fenómenos debe analizarse y debe documentarse, para habilitar una comprensión en la dinámica y los factores asociados con el aumento de estos eventos en el Pacífico costarricense

Proliferaciones algales de la diatomea toxigénica Pseudo-Nitzschia (Bacillariophyceae) en el Golfo de Nicoya, Costa Rica / Algal blooms of the toxigenic diatom Pseudo-Nitzschia (Bacillariophyceae) in the Golfo de Nicoya, Costa Rica

En el mes de noviembre de 2001, se aisló de una marea roja cerca de la Isla San Lucas, las diatomeas Pseudo-Nitzschia pungens f. pungens seguida por Skeletonema costatum, Chaetoceros lorenzianus y en menor concentración Thalassiosira spp. las cuales fueron caracterizadas por microscopía electrónica de rastreo y transmisión, siendo esta la primera vez que se describe la presencia de estas especies produciendo proliferaciones en Costa Rica. Actualmente existe un aumento en el reporte de mareas rojas donde predominan las diatomeas, y los conteos celulares indican el aumento en el número de las especies conocidas como Pseudo-nitzschia pungens f. multiseries. A estas se les atribuye la producción del ácido domóico, un aminoácido de bajo peso molecular. Las intoxicaciones amnésicas por mariscos (IAM) que afectan a los humanos, se producen por la ingesta de mariscos contaminados con este ácido. En Costa Rica, hasta la fecha, solo se han reportado casos de intoxicación paralítica por mariscos contaminados por los dinoflagelados Pyrodinium bahamense var. compressum y Gymnodinium catenatum, sin embargo existe la posibilidad de producirse intoxicaciones humanas por la ingesta de mariscos y peces contaminados con toxinas amnésicas las cuales son hidrosolubles y termoestables. Debe entonces considerarse el peligro potencial de aparición de casos de intoxicaciones amnésicas y se sugiere la inclusión de estas especies en los programas de monitoreo permanente para tomar las medidas preventivas de salud pública

Water samples were collected during a red tide event in November 2001, near San Lucas Island (Gulf of Nicoya, Costa Rica). Superficial temperature was 27ºC and water was turbid, with no fetid smell. One sample was treated with negative staining and observed using a transmission electron microscope (TEM); another sample was observed using a scanning electron microscope (SEM). Samples had high concentrations of the diatom Pseudo-Nitzschia pungens f. pungens (characterized by two rows of poroids in the external channel), and lower concentrations of Skeletonema costatum (chains joined by external microtubules) and Chaetoceros lorenzianus (oval apertures and long chains, having setae with distinctive transverse rows and spines). This is the first time that the first species was described producing red tides in Costa Rica. However, reports about red tides with high concentration of species like P. pungens (variety multiseries) are increasing. These species have been related to the production of domoic acid, a low molecular weight amino acid which in humans can cause amnesic intoxications with seafood. Previously, Costa Rican reports of toxic accidents only referred to seafood contaminated with Pyrodinium bahamense var. compressum and Gymnodinium catenatum dinoflagellates. The increase in the number of Pseudo-Nitzschia causing harmful algae blooms is of interest for scientists around the world and must be documented. Similarly, some Chaetoceros species have been reported to be harmful to fish. We strongly recommend the establishment of a permanent surveillance program monitoring the presence of these species new at Costa Rican Pacific coast. Since the amnesic toxin is soluble in water and heat-resistant, we want to stress the possibility of having human cases of amnesic intoxication

Paralytic shellfish toxins in the chocolata clam, Megapitaria squalida (Bivalvia: Veneridae), in Bahia de La Paz, Gulf of California

Occurrence and toxic profiles of paralytic shellfish toxins (PST) in the chocolata clam Megapitaria squalida were investigated. From December 2001 to December 2002, 25 clams were obtained monthly from Bahía de La Paz, Gulf of California. Additionally, net (20 µm) and bottle phytoplankton samples were also collected to identify toxic species. Toxins were analyzed by HPLC with post-column oxidation and fluorescence detection. Toxicity in the clam was low and varied from 0.14 to 5.46 µg/STXeq/100 g. Toxicity was detected in December, March, April, June, and August. Toxin profile was composed mainly by STX, GTX2, GTX3, dcGTX2, dcGTX3, C2, dcSTX and B1. Gymnodinium catenatum was the only PST-producing dinoflagellate identified in the phytoplankton samples throughout the study period. G. catenatum was observed mainly in net samples from December 2001 to December 2002; however, in bottle samples, G. catenatum was only observed in five months. Highest abundance (2 600 cells l-1 ) was observed in March and the lowest (160 cells l-1 ) in June. G. catenatum mainly formed two-cell chains and rarely four or eight. The presence of PST in net phytoplankton samples support the fact that G. catenatum is the main source of PST in the clams. This study represents the first report of PST toxins in the chocolata clam from Bahía de La Paz

Se investigó la ocurrencia así como los perfiles de toxinas paralíticas (PST) en la almeja chocolata Megapitaria squalida (Sowerby, 1835), de la cual se recolectaron mensualmente 25 ejemplares de diciembre del 2001 a diciembre del 2000 en La Bahía de La Paz, Golfo de California. Simultáneamente, se obtuvieron muestras de fitoplancton de botella y de red (20 µM) para identificar especies tóxicas, así como para detectar la presencia de toxinas paralíticas. Las toxinas se analizaron por HPLC con una oxidación post-columna y detección fluorescente. La toxicidad en las almejas fue baja y varió de 0.14 a 5.46 µg/STXeq/100 g y se detectó en diciembre, marzo, abril, junio y agosto. El perfil de toxinas estuvo compuesto principalmente por STX, GTX2, GTX3, dcGTX2, dcGTX3, C2, dcSTX y B1, siendo similar al perfil observado en las muestras de red. Gymnodinium catenatum fue la única especie productora de toxinas paralíticas identificada en las muestras de fitoplancton a través de todo el período del estudio. G. catenatum se observó principalmente en muestras de red correspondientes a diciembre 2001-diciembre 2002; sin embargo, en muestras de botella, G. Catenatum solo fue observado en cinco meses. La abundancia más alta (2 600 céls l-1 ) se encontró en marzo y la más baja (160 céls l-1 ) en junio. G. catenatum se presentó formando cadenas de dos células y raramente de cuatro u ocho. La presencia de toxinas en las muestras de red donde esta especie es frecuente, apoya la idea de que G. catenatum sea la fuente principal de PST en las almejas. Este estudio representa el primer reporte de toxinas paralíticas en la almeja chocolata de Bahía de La Paz

Pertubacion quimica sobre la estructura del fitoplancton en un estanque artificial (Guaicaipuro, Edo. Miranda, Venezuela) / Chemical disturbance of the Phytoplankton structure in an artificial pond (Guaicaipuru, Edo. Miranda, Venezuela)

Cuando un ecosistema sufre una perturbación externa, éste se revierte a un estado sucesional temprano, caracterizado por cambios en la función y estructura de la comunidad, pudiéndose anticipar las respuestas del ecosistema ante un estrés. Los propósitos fundamentales del trabajo fueron cuantificar el efecto de una pertubación por un compuesto químico (Sulfato de Cobre, a 100 mug L(-1) granulado, al 93 por ciento, de la casa Proquim) en la comunidad del fitoplancton en un estanque ubicado en Guaicaipuro, Edo. Miranda (Venezuela), y comparar la composición y diversidad de la misma antes y después de la aplicación. Así mismo, comprobar la hipótesis planteada por Odum sobre la respuesta de la comunidad al estrés químico. El químico se aplicó en diferentes puntos al azar para aseguar que se distribuyera en forma homogénea en el estanque. Una sola aplicación del químico se realizó 6 horas después de la toma de la primera muestra. Se realizaron mediciones de oxígeno disuelto en la superfície y fondo. Para la estimación del fitoplancton se tomaron muestras de agua nterdiaria en forma directa en 5 puntos al azar, hasta completar 2 litros, durante 30 días, al comienzo del período de lluvia, entre los meses de junio y julio de 1994. El oxígeno disuelto varió con un máximo en la superfície de 9,3 mg O2/L y un mínimo en el fondo de 2,3 mg O2/L. La riqueza de especies varió entre 4 y 18. El fitoplancton entre 7,1 x 10(4) y 7,8 x 10(6) cel/L. El índice de Diversidad entre 0,12 y 1,39. Los valores mínimos de oxígeno riqueza de especies y fitoplancton se observaron el quinto día después de agregar el químico. Antes de la aplicación, el fitoplancton estuvo dominado por algas filamentosas, principalmente por las Chlorophyta. Después del tratamiento se observó una disminución en la abundancia de individuos, del número de especies y un aumento de individuos de menor tamaño. Al séptimo día aparecieron en abundancia las Cyanobacteria del Orden de las Chroococcales, revirtiendo la comunidad a estados tempranos de una sucesión ecológica. Desde el noveno día, se observaron secuencias de abundancias en el siguiente orden: Chrysophyta, Pyrrophyta, Bacillariophyta y Euglenophyta, con un aumento en la riqueza de especies. Al final del período comenzaron a Aparecer las Chlorophyta filamentosas. Los resultados obtenidos sobre las tendencias del ecosistema ante un estrés químico, soportan las hipótesis de Odum.

Impact of pollution on phytoplankton structure and bacteria in some Alexandria beaches, Egypt

The hydrographic, phytoplankton and bacteria data were collected monthly during 1995 from nine selected beaches of Alexandria, as an attempt to classify Alexandria recreational areas. The results showed a distinct difference between the water quality of Eastern and western parts of beaches in all parameters. Generally, relatively high values of water salinity, low concentration of nutrient salts particularly ammonia, nitrite and silicate as well as low oxidizable organic matter are considered as indicators of improvement in the water quality. The phytoplankton standing crop displayed wide variation, from 9 x 103 to 20.5 x 106 unit.L-1 chlorophyll-a content from 0.01 to 12.7 mg.m-3, Coliform bacteria from 0.0 to 2600 per 100 ml and diversity from 0.09 nats to 2.57 nats. The phytoplankton comprised 102 taxa belonging to a wide ecological habitat, extending from fresh water forms [33 species] to typical marine forms [69 species] often found side by side. However, few of them were responsible for the bulk of the community; namely, Skeletonema costatum, Rhizosolenia fragilissima, R. delicatula, R. hebetata, Nitzschia seriata, Chaetoceros socialis and Euglena granulata. The highest distribution of phytoplankton standing crop, chlorophyll-a and bacteria counts as well as low diversity values were recorded at a highly eutrophic area, Shatby and Anfoushi beaches. Monthly variation showed the highest outstanding peak in summer months. Several phytoplankton species were recorded as indicators of eutrophication. The correlation between phytoplankton standing crop, chlorophyll-a content, diversity, bacteria counts and the environmental conditions at each beach were computed and discussed

Physiological responses of the cyanobacterium calothrix parietina and green alga scenedesmus dimorphus to iron, manganese, sulphate and sulphite

The uptake of manganese and iron ions by Scenedesmus dimorphus and Calothrix parietina was significantly increased by increasing the doses supplemented to the culture media of both algae up to 10[-5]molar concentration. The ability of Scenedesmus to accumulate the two metals was greater than that of Calothrix. Higher concentrations of sulphate, sulphite and manganese ions inhibited the accumulation of total carbohydrates in the two phytoplankter cells. All iron levels stimulated synthesis of total carbohydrates in Calothrix, but inhibited it in Scenedesmus. Under all concentrations of the four pollutant salts, nitrogen secretion by the two organisms, total nitrogen and almost all nitrogen fractions were increased particularly at moderate rates. However, 10[-4] M and 300 micro g S ml[-1] of iron and sulphite attenuated the synthesis of protein N in Calothrix, Sulphate, sulphite and iron suppressed phosphorus uptake by Calothrix but stimulated it in Scenedesmus. Manganese ions at all concentrations, encouraged phosphorus uptake from nutrient media by Calothrix. Sulphite, at al concentrations lowered total phosphorus content, total soluble and total insoluble phosphorus in the two organisms, a phenomenon that was associated with marked disturbances in phosphorus metabolism. Sulphite, at all concentrations inhibited the biosynthesis of nucleic acids [RNA, DNA] in Calothrix, while its low and moderate concentrations stimulated their biosynthesis in Scenedesmus. Sulphate and manganese on the other hand, stimulated their biosynthesis in the two phytoplankters. Iron, at 10[-8] M level encouraged the biosynthesis of nucleic acids in Calothrix, whereas 10[-6] M and 10[-4]M concentrations suppressed their formation in Scenedesmus. At all levels of manganese and sulphate, the cell length and width of both organisms and the diameters of heterocyst in Calothrix were increased. At all concentrations of iron and sulphite, the cell length and width of both organisms and also diameters of heterocysts in Calothrix were decreased